Mark H Harris <harrismh...@gmail.com> writes: > On 5/11/14 12:05 PM, Alain Ketterlin wrote: >>> Julia is Matlab and R, Python, Lisp, Scheme; all rolled together on >>> steroids. Its amazing as a dynamic language, and its fast, like >>> lightning fast as well as multiprocessing (parallel processing) at its >>> core. Its astounding, really. >> >> Hmmm... >> >>> Its number concept is unified, >> >> What exactly is unified? There is no implicit promotion between >> primitive types and BigInt/Float. > > > The built-in math functions (extensive, by the way) just work, and > they work consistently the way you might expect across types. Consider > sqrt(): [...] > You'll notice that I did not need to import anything to use sqrt(), > and sqrt() takes all types and does something meaningful with them.
Sorry, i wasn't clear enough: "doing something meaningful with them" is precisely where the problem is. Every single operation requires multiple-dispatch (i.e., dynamically testing types, converting to a common type, and selecting the version of sqrt to use). That's probably more than the time it takes to actually perform the computation, a bit like what happens with x+y on integers with Python, where only a fraction of time is spent on adding integers. When you are doing scientific computation, this overhead is unacceptable, because you'll have zillions of computations to perform. Julia provides a way to make things fast: typing. If you provide explicit types, the dynamic typing part obviously disappears, and the overhead is removed. But then, you're not too far from Fortran, or C/C++. > The following code will produce over 100,000 digits of π (pi) in less > than 2 seconds on a low-end processor, like my mac mini dual core > 2Ghz: You seem to be discovering the power of the libraries that are behind all this (MPFR in that case)... [...] > But, like lisp, Julia's internal structures are lists, so, it can > create and modify its own code on-the-fly. [...] Sorry, I was comparing to Fortran, and it's use in scientific computing. Self modifying code is totally irrelevant there. -- Alain. -- https://mail.python.org/mailman/listinfo/python-list
